Rotary high current pick-off

ABSTRACT

An electric conductor comprising two electrically conducting members at least one of which is rotatable. Both members are in contact with an electrically conducting liquid consisting of a metal or alloy having a melting point in the range of 0* to 150*.

United States Patent Tole et a]. Apr. 10, 1973 [5 ROTARY HIGH CURRENT PICK-OFF References Cited [75] Inventors: Walter Roland Tole, High UNITED STATES PATENTS wycombe; Ky'iakis 2,424,545 7 1947 Bard ..339 118 RY x wembley, both of England 2,889,531 6/1959 Ellerman et al.... ..339/5 1. 3,0 ,496 2 1962 K ..3 9 ll RY [73] Instrument cmpany 3,3 3,865 11968 a 1 1811? High Wycombe, Buckinghamshire, 3,431,532 3 1969 Cary ..339/5 1. x England I F APPLIC Filed: Dec. 1970 OREIGN PATENTS OR ATIONS 777,335 6/1957 Great Britain ..339/8 L 1 pp N91 96,857 146,846 9/1962 U.S.S.R ....339/8 L Primary Examiner-Richard E. Moore [30] Forelgn Application Pnonty Data 7 Att0rney-Whittemore, Hulbert & Belknap Dec. 10, 1969 Great Britain ..60,335/69 [57] ABSTRACT 1 18 339/278 C An electric conductor comprising two electrically con- [51] Int. Cl. ..H01r 39/30 ducting members at least one of which is rotatable. [58] Field of Search ..339/5, 8, l 18, 278 C Both members are in contact with an electrically con.-

ducting liquid consisting of a metal or alloy having a melting point in the range of 0 to 150.

3 Claims, 1 Drawing Figure ROTARY HIGH CURRENT PICK-OFF The present invention relates to a device for passing an electric current from a rotating electrically conducting member to a stationary or another rotating electrically conducting member.

Conventional systems using brush and slipring assemblies suffer from frictional torque and brush/slipring wear particularly in pick-offs of high current capacity, i.e., 10 to 50,000 Amps.

It is known to use a mercury bath for electrically connecting the two conducting members. This of course eliminates the need for brush and slipring assemblies. However, since mercury vapor is extremely toxic the use of mercury can be highly dangerous and in certain countries its use is prohibited by legislation.

An object of this invention is to provide a device for carrying an electric current between two electrically conducting members, one of which is rotatable, which has the advantages of using mercury without the disadvantages.

The invention provides a device for carrying an electric current between a first rotatably mounted electrically conducting member and a second electrically conducting member, wherein an electrically conducting metal or alloy is provided having a melting point in the range to 150C, both electrically conducting members being in contact with the liquid.

In one embodiment of the invention, the second electrically conducting member is rotatably mounted.

The electrically conducting members may be pulleys, discs, wheels, shafts, spindles, spheres, drums etc.

Preferably, the resistance between the two electrical conducting members via the electrically conducting liquid is in the range 0.00] micro-ohms to 1 ohm.

The invention will be further described with reference to an embodiment shown in longitudinal sec- The bearings 5 and 6 are mounted in electrically insulating sleeves 8 and 9 in order to eliminate any electric current from flowing through the bearings.

The electrically conducting shafts l and 2 are electrically connected through an electrically conducting liquid metal 10 which is trapped in a space between the other ends of the shaft 1 and 2 by O-ring seals 11 mounted on the bearing 12. The space containing the liquid 10 is of such configuration that the electrical path between rotary and stationary elements has a resistance in the range 0.001 micro-ohms to 1 ohm. The electrically conducting liquid metal 10 is a metal, or metal alloy, of low resistivity and has a melting point in the range of 0-l50C. An electrical heating element 13 is provided to maintain the liquid metal 10 at the requisite melting point. Because the heating element 13 rotates together with a shaft 1, small brushes l4 and sliprings 15 are provided to supply electric current to the heating element 13.

Alternative forms of heating elements may be used such as a radiant heater, hot air blowers, steam jackets, hot liquid baths, flame heaters and the like. These offer the additional advantage that no brushes or sliprings are required.

An expansion chamber 16 is provided to allow for expansion of the electrically-conducting liquid metal 10.

A greasing duct 17 is provided in the shaft 2 in order to provide lubrication for the seal bearing 12.

The following is a list of suitable alloys which are suitable for use in the above-described device:

1. Alloy of bismuth, lead, tin, cadmium, indium.

2. Alloy of bismuth, lead, tin, indium.

3. Alloy of bismuth, lead, tin, cadmium.

4. Alloy of bismuth, lead, tin, cadmium.

5. Alloy of bismuth, lead, tin.

6. Alloy of bismuth, tin, indium.

7. Alloy of bismuth, tin, cadmium.

The metals in the above-mentioned alloys may be present in different proportions to provide a melting point within the range 0150C.

For example in alloys 1 to 5 preferably, the amounts of lead and tin are 60 percent and 38 percent by weight, respectively, although these amounts may vary.

We claim:

1. An electric conductor comprising a first electrically-conducting member, a second electrically conducting member, said second electrically conducting member being rotatable relative to said first electrically conducting member, and an electrically conducting material being in contact with both of said electrically conducting members, the said material consisting of a metal'or alloy having a melting point in the range of 0 to C., and heating means independent of the material for heating said material to its melting point to liquefy the material, said heating means comprising an electrical resistance heating element mounted on one of said members.

2. An electric conductor as claimed in claim 1,

wherein the resistance between the two electrically 1 conducting members via the electrically conducting liquid is in the range 0.001 micro-ohms to 1 ohm.

3. An electric conductor comprising a first electrically conducting member, a second electrically conducting member, said second electrically conducting member being rotatable relative to said first electrically conducting member, and an electrically conducting material being in contact with both of said electrically conducting members, the said material consisting of a metal or alloy having a melting point in the range 0 to 150 C., and means independent of the material for heating said material to its melting point to liquify the material, both of said members being rotatable shafts, one of said shafts being hollow throughout its major portion and open at one end and closed at its other end, the other of said shafts extending into the open end of said first shaft and having an inner end spaced closely from the closed end of said one shaft, said material being confined in a space including the space between the closed end of said one shaft and the inner end of said other shaft, said other shaft having a bearing portion spaced from its inner end, a bearing carried within said one shaft engaging the bearing portion of said other shaft, and sealing means associated with said bearing to confine said material within the space adjacent the closed end of said one shaft, the inner end of said other shaft having an expansion chamber therein to allow expansion of said material. 

2. An electric conductor as claimed in claim 1, wherein the resistance between the two electrically conducting members via the electrically conducting liquid is in the range 0.001 micro-ohms to 1 ohm.
 3. An electric conductor comprising a first electrically conducting member, a second electrically conducting member, said second electrically conducting member being rotatable relative to said first electrically conducting member, and an electrically conducting material being in contact with both of said electrically conducting members, the said material consisting of a metal or alloy having a melting point in the range 0* to 150* C., and means independent of the material for heating said material to its melting point to liquify the material, both of said members being rotatable shafts, one of said shafts being hollow throughout its major portion and open at one end and closed at its other end, the other of said shafts extending into the open end of said first shaft and having an inner end spaced closely from the closed end of said one shaft, said material being confined in a space including the space between the closed end of said one shaft and the inner end of said other shaft, said other shaft having a bearing portion spaced from its inner end, a bearing carried within said one shaft engaging the bearing portion of said other shaft, and sealing means associated with said bearing to confine said material within the space adjacent the closed end of said one shaft, the inner end of said other shaft having an expansion chamber therein to allow expansion of said material. 